1. Field of the Invention
The invention relates to a self-pumping hydropneumatic shock absorbing spring leg or strut with internal lever regulation or control, in particular, for motor vehicles.
2. Background of the Invention
Known versions of such devices include a working cylinder filled with oil or a damping medium, which oil or damping medium is under the pressure of at least one gas cushion located in a high pressure chamber. Such a device may act as a spring. The working cylinder is often divided by a piston into two working chambers. The piston is often supported by a hollow piston rod. The hollow piston rod includes a piston pump which is driven by the movements of the device or spring to transport the oil or damping medium from a low pressure chamber into the working chamber, which working chamber is connected to the high pressure chamber. The pump cylinder of the piston pump is formed by the hollow piston rod, into which piston rod extends a hollow pump rod which is fastened to the work cylinder and has a suction valve on its forward end. The hollow pump rod is connected to the low pressure chamber and connected with a deregulation chamber having a deregulation opening which can be closed as a function of the position of the piston in the working cylinder. The deregulating opening connects the working chamber, which working chamber is, in turn, connected with the high pressure chamber, with a deregulation passage having a throttle and empties into the low pressure chamber.
Self-pumping hydropneumatic shock absorbing struts, such as those disclosed in German Laid Open Patent Appln. No. 36 30 757, are already known. In such devices, during the travel of the vehicle, oil or damping medium is pumped into the working cylinder via the piston pump of the shock absorbing strut until the vehicle reaches a standard elevation. After the standard elevation has been reached, the working cylinder releases or exposes a deregulating opening so that, with the use of a short circuit or by-pass, further height adjustment of the vehicle body can be avoided. It is a disadvantage of this type of shock absorbing strut that, during the loading of the vehicle, the vehicle body is not brought up to the standard elevation immediately after the start of the vehicle but that the upward adjustment only occurs after a certain driven distance. The driven distance is required for the piston pump to transfer sufficient oil or damping medium into the working cylinder.